A few days ago I read an article about repetitive injury and how maybe you shouldn't run only on the sidewalk. It talked about how all the little muscles in your feet, legs, etc got a workout if you ran on other surfaces. I know this to be true because of hiking--no matter how much I've been walking, hiking is always a different workout--I can really feel it in my feet, legs, back, butt, etc.
I did run a little on the asphalt last time but of course that doesn't do much except add the tiniest bit of cushion to your body. So today I ran on grass, concrete sidewalk, and asphalt. Oh my. I ache from the waist down! The grass really kicked my butt. The first time it was GREAT--it felt so good to my feet and my body. I felt like I was springy! But as the run wore on (keep in mind I'm STILL doing Week 1 in the Couch to 5K program) I could really feel it from the waist down. By the end I was back to slogging along slowly in my run. It probably didn't help that I didn't give myself one extra day before going out again. My mind said, "GO! It's going to snow tomorrow!" I wasn't completely recovered from Saturday's run.
Overall I feel sore but not like I've messed anything up (knock on wood).